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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727662118; bh=OUonpseR6pJPGe8VGSeGWmeUScOwYYqu4kkrnSeXGf0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=bvhEU7jz/GlZS2Y5SRMHRqC00fg3ROMhjb2IVGCdCoSygbQ8ybdXoDL2gJhL6N+SM qypDZIx81N51BvC/0Dm+8K24kPENXEPk+VNqg6cZtQSdxSqhTbc+6u5lFVNH7TNMVm vmec0sC+P/O5KS2eclw4dtkkx5EU3NBJG52uL3eleQQ4CpX+puai5/w0oX0ls4vBuk LNOI7ilAKPtv7UljqNZquY8k11WAR4knhRGUNa5WqskwAtADNNX1j3kqv35jiQtjh4 //g6utAwDxQBzWW6xWB6gtXbd6X0ECtfi6dxmiimC64og2quy2Orwh6Kdg63QXKxGF aMUhEVPfMp1RQ== Date: Sun, 29 Sep 2024 19:08:34 -0700 From: Namhyung Kim To: Alexei Starovoitov Cc: Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , John Fastabend , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , LKML , bpf , Andrew Morton , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm , Arnaldo Carvalho de Melo Subject: Re: [RFC/PATCH bpf-next 1/3] bpf: Add kmem_cache iterator Message-ID: References: <20240927184133.968283-1-namhyung@kernel.org> <20240927184133.968283-2-namhyung@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 8FB7080004 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: bb6tz8zs894zh7tqmfstqnyx8hbni71i X-HE-Tag: 1727662119-663860 X-HE-Meta: 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 R99QfaZQ 3DPGCU5i37hiUOkvchcphCn+AR1fm6brRcFGulVcyW5T3Fyj0o3U0lUKUNeYSM6ZIOQuXtrlr8PMwmYLgRsFd4O2EKFlyGHosOTLw+gNfwmS3JvBurq5n2WOju8XOBlgeOfwM7Gsbqngd9djWnrTGv/+bEB0xEL0Rib8rzOYwVuRyN30xXtAuACbFlEefEDvX5BlbyM6j/z3kpocBTIovgpJlg0783VrZD/Au495d0fQVZ61rrQD7jZgFEBkNmRP+KODWNQc9e5tj6fFBjRkLm3q+rhZ1O1yrDpzPPc6XOyKI1AKj78pcLGROTfUXzcNf2oADPCNVbXuvoFim2SgRaELbXj74/EWIhUas52X4ckq4pLDBPe4P3tglVg+RhBHh3nSVquP5dBrdXO0OVLaSHftjfDqLc5FCNyu8qDE0ADRZ02KV13elMFkIGw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Sun, Sep 29, 2024 at 10:04:00AM -0700, Alexei Starovoitov wrote: > On Fri, Sep 27, 2024 at 11:41 AM Namhyung Kim wrote: > > +static void *kmem_cache_iter_seq_start(struct seq_file *seq, loff_t *pos) > > +{ > > + loff_t cnt = 0; > > + struct kmem_cache *s = NULL; > > + > > + mutex_lock(&slab_mutex); > > It would be better to find a way to iterate slabs without holding > the mutex for the duration of the loop. > Maybe use refcnt to hold the kmem_cache while bpf prog is looking at it? Do you mean that you want to not hold slab_mutex while BPF program is running? Maybe we can allocates an arary of pointers to the slab cahe (with refcounts) at the beginning and iterate them instead. And call kmem_cache_destroy() for each entry at the end. Is it ok to you? Thanks, Namhyung